Many people write to me, asking "what is the 'best' thyroid drug?" There are also constant debates on my thyroid forums, with people arguing that they think Armour is the best, or Synthroid is the best, or Thyrolar, or Levoxyl, etc. And of course, most thyroid patients who have asked a doctor to switch from one thyroid drug to another has probably encountered resistance, in the form of a firm belief that one particular drug is "better" than another.

Who is right? Is a particular drug best? Are some drugs better than others? How do you know which one is best for you?

Some thyroid patients do best on levothyroxine products. And frequently, given that this is the conventional medical world's sanctioned approach, most patients will find themselves at least starting with levothyroxine.

Levothyroxine is the synthetic form of thyroxine (T4), one of the two main hormones the thyroid produces. The most widely prescribed levothyroxine product is the brand Synthroid. Synthroid has regularly claimed to be better than its competitors, but research proved them to be bioequivalent -- or equal, in terms of what function they perform in the body -- to their competition, so this claim of superiority actually has no merit. Many doctors, however, still erroneously believe that Synthroid is "better," after being subject to years of this misleading advertising message. Synthroid also tends to be more expensive than the competitive levothyroxine drugs.

Five years after the FDA required all levothyroxine products to file new drug applications, on July 24, 2002, Synthroid finally obtained FDA approval, making it the fourth levothyroxine to obtain the FDA's approval, after the August 2000 approval of Unithroid, Levoxyl's May, 2001 approval, and Levo-T's 2002 approval.

All the levothyroxine products, Synthroid, Unithroid, Levoxyl and Levothroid, have different fillers and binders, so people may have different allergic responses to the different brands. (Levoxyl is also fast-dissolving, and should be taken with sufficient water, and swallowed quickly to maximize absorption.) If you react to one levothyroxine, your doctor might want to try other brands to see if you react to those brands as well.

Some people who are on levothyroxine also need the addition of the second key hormone, triiodothyronine (T3).Among that group, some people do best with the synthetic T3 drug Cytomel. (Anecdotally, however, some patients have reported allergic reactions to Cytomel.) The option, compounded or time-released compounded synthetic T3, has been used successfully by some patients.

Other doctors and patients prefer a product known as Thyrolar, a synthetic combination of T4 and T3.

Some patients do best on natural desiccated thyroid drugs, such as Armour thyroid, or, in some cases, people find the hypoallergenic formula of natural drug, Nature-throid, works best for them. Pork allergies or religious prohibitions against pork may make these products problematic for some patients. There are some patients and practitioners who are also concerned about these products due to fears of prion-related diseases such as Mad Cow Disease, despite manufacturer assurances that these products are safe.

So is one of these products better than the other? I think Dr. Richard Shames, a holistic physician and author of ThyroidPower and Fat, Fuzzy and Frazzled , who has treated thyroid conditions for a quarter century, has the best advice for patients.

"In 25 years of practice, I have found that it doesn't necessarily matter which kind of thyroid hormone you start with so much, as which kind you end up with after trying several different types to see which one works best for you. Initially, I typically recommend whatever type they have either heard about, have a "gut-feeling" about, know family members who have a good response to a particular kind of medicine, or have a philosophical inclination for one kind or another. Sometimes it it the combination of two or three of the above medicines that proves to be the magic solution for a particular person. If the initial item tried does not give 85-95% improvement, I then encourage the person to either add something to their first choice product or discontinue it and start something totally new. It is my firm belief that the state of the art in finding the optimal medicine is still trial and error."

As a patient advocate, I can tell you, there is no miracle answer. If I were to tell you that only one drug works for everyone, I would be as narrow-minded and simplistic as the endocrinologists whose slavery to Synthroid I regularly condemn. So...the answer is, the best drug is the drug which safely makes you feel your best. And there's no predetermined formula to tell which drug will be the best for you, until you try them, find optimal doses, and see how you do over time.

For detailed information on thyroid hormone replacement drugs, how to find the best one for you, and how to find a doctor willing to try different drugs with you, read the 2005 revised Second Edition of my best-selling book Living Well With Hypothyroidism. (ORDER FROM AMAZON.COM NOW.)

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